package com.example.Sao.Tools;

import java.io.UnsupportedEncodingException;

public class ByteUtil
{
    private static final String TAG = "StringUtils";
    private static long messageId = 0;
    /**
     * byte[] �?int
     * @return
     */
    public static int bytesToInt(byte[] bytes, int startPos, int length)
    {
        byte[] temp = new byte[length];
        System.arraycopy(bytes, startPos, temp, 0, length);
        int fromByte = 0;
        for (int i = 0; i < 4; i++)
        {
            int n = (temp[i] < 0 ? (int) temp[i] + 256 : (int) temp[i]) << (8 * (3 - i));
            fromByte += n;
        }
        return fromByte;
    }


    /**
     * byte[] 转short
     * @param b
     * @return
     */
    public static short bytesToShort(byte[] b, int startPos, int length)
    {
        byte[] temp = new byte[length];
        System.arraycopy(b, startPos, temp, 0, length);
        return (short) (temp[1] & 0xff | (temp[0] & 0xff) << 8);
    }

    /**
     * byte[] �?String UTF-8编码
     * @return
     */
    public static String bytesToString(byte[] bytes, int startPos, int length)
    {
        byte[] temp = new byte[length];
        System.arraycopy(bytes, startPos, temp, 0, length);
        String returnStr = "";
        try
        {
            returnStr = new String(temp, "UTF-8");
        }
        catch (UnsupportedEncodingException e)
        {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return returnStr;
    }
    public final static byte[] getBytes(short s)
    {
        byte[] buf = new byte[2];
        for (int i = buf.length - 1; i >= 0;i--)
        {
            buf[i] = (byte) (s & 0x00ff);
            s >>= 8;
        }
        return buf;
    }

    public final static byte[] getBytes(int s)
    {
        byte[] buf = new byte[4];
        for (int i = buf.length - 1; i >= 0; i--)
        {
            buf[i] = (byte) (s & 0x000000ff);
            s >>= 8;
        }
        return buf;
    }

    public static String bytesToHexString(byte[] src){
        StringBuilder stringBuilder = new StringBuilder("");
        if (src == null || src.length <= 0) {
            return null;
        }
        for (int i = 0; i < src.length; i++) {
            int v = src[i] & 0xFF;
            String hv = Integer.toHexString(v);
            if (hv.length() < 2) {
                stringBuilder.append(0);
            }
            stringBuilder.append(hv);
        }
        return stringBuilder.toString();
    }

    public static byte[] hexStringToBytes(String hexString) {
        if (hexString == null || hexString.equals("")) {
            return null;
        }
        hexString = hexString.toUpperCase();
        int length = hexString.length() / 2;
        char[] hexChars = hexString.toCharArray();
        byte[] d = new byte[length];
        for (int i = 0; i < length; i++) {
            int pos = i * 2;
            d[i] = (byte) (charToByte(hexChars[pos]) << 4 | charToByte(hexChars[pos + 1]));
        }
        return d;
    }

    private static byte charToByte(char c) {
        return (byte) "0123456789ABCDEF".indexOf(c);
    }


    public static short bytesToShort2( byte[] b, int startPos, int length )
    {
        int mask = 0x000000ff;
        int temp = 0;
        short n  = 0;

        for( int i=0; i<2 && i<length; i++ )
        {
            n   <<= 8;
            temp  = b[startPos+i] & mask;
            n    |= temp;
        }

        return n;
    }
    public static int bytesToInt2( byte[] b, int startPos, int length )
    {
        int mask = 0x000000ff;
        int temp = 0;
        int n    = 0;

        for( int i=0; i<4 && i<length; i++ )
        {
            n   <<= 8;
            temp  = b[startPos+i] & mask;
            n    |= temp;
        }

        return n;
    }
    public static long bytesToLong2( byte[] b, int startPos, int length )
    {
        int  mask = 0x000000ff;
        int  temp = 0;
        long n    = 0;
        for( int i=0; i<8 && i<length; i++ )
        {
            n   <<= 8;
            temp  = b[startPos+i] & mask;
            n    |= temp;
        }

        return n;
    }


}
